list_calendars

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries full burden. It discloses return fields (calendarId, name, supported event types) which compensates for the missing output schema. However, it omits safety characteristics (read-only), idempotency, or rate limiting that would help an agent understand operational constraints.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two efficiently structured sentences with zero waste. First sentence establishes scope with examples; second sentence discloses return values. Information is front-loaded and appropriately sized for the tool's simplicity.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's low complexity (no parameters, simple list operation) and absence of output schema, the description adequately covers return values. It could be improved by noting that no authentication parameters are required (since iCloud auth is implicit), but this is sufficient for agent selection.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema contains zero parameters. According to scoring rules, 0 parameters establishes a baseline score of 4. The description does not need to compensate for parameter documentation gaps.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses specific verb 'List' with resource 'calendars' and context 'iCloud Calendar'. Examples (Personal, Work, LSAT PREP) clarify scope. It clearly distinguishes from sibling 'list_events' by targeting calendar containers rather than individual events.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage through the return value disclosure (calendarId), suggesting it's for discovering available calendars. However, it lacks explicit guidance on when to use this versus 'list_events' or prerequisites like 'use this first to get calendarIds before creating events'.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.